Traditionally, the nuclear reactor of a pressurized water reactor comprises a vessel and a core positioned inside the vessel. The core includes nuclear fuel assemblies, each assembly extending in an axial direction, preferably vertically. Each assembly includes nuclear fuel rods and grids designed to maintain the positioning of the rods and/or to ensure mixing of the coolant fluid, and is spaced apart from another assembly by a clearance following a transverse direction perpendicular to the axial direction. The rods each include a sheath containing nuclear fuel pellets.
The fuel, such as pressurized water, flows inside the vessel, for example by rising inside the latter to the core, to be heated therein while ensuring the refrigeration and moderation in the core.
One recurring need is to simulate, by a computer and as precisely as possible, the flow of the fluid inside the vessel, for example to improve the computation of a mechanical deformation of the assemblies of the core during operation of the reactor, while not requiring an excessive computing power. The deformations of the assemblies are in fact likely to disrupt the operation and performance of the reactor: risk of incomplete insertion of control clusters, which make it possible to adjust the reactivity of the core of the nuclear reactor, or unacceptable increase in their drop time, risk of local variation of the moderation of the core, etc. During handling, for example during unloading and reloading operations of the core for maintenance, these deformations increase the risks of catching between the fuel assemblies. A better modeling of these deformations is therefore sought in order to resolve these issues, or at least to define palliative measures.
Document KR 100 957 066 B1 describes a method for modeling a nuclear reactor core implementing a digital mechanical computation of the fluids, also called CFD (Computational Fluid Dynamics). The model of the core is based on a porous model.
Document KR 100 957 061 B1 describes a safety analysis method for a nuclear reactor implementing hydraulic computations from head loss coefficients.
However, the simulation of the flow of the fluid inside the vessel is not optimal, homogenous modeling of the core not making it possible to determine the deformations of the fuel assemblies. Furthermore, this modeling requires an excessive computing power to be able to be implemented with the current computation means.